Duplicating stencil



Cil

Patented Sept. 21, 1926.

UNITED STATES.

HEINRICH HARTMANN, CF HANOVER, GERMANY.

DUPLICATING STENCIL.

No Drawing. Application filed December 18, 19525,

This invention relates to improvements in and in the production of stencil sheets such as used in the duplication or manifolding of typewritten matter or designs or handwritten matter marked on the stencil sheet by means of a suitable scribel tool. The object of this invention is to produce a stencil sheet which can be used withoutany preparatory treatment, can be stored for some time before use and without danger to the coating and in addition will enable theproduct-ion of large numbers of duplicates with a clear well defined outline.

In addition to the well known waxed paper stencils, it has been known for some years to use a thin and fine Japanese paper coated with a layer of a protein. As known, the preparation of the stencil consists in removing the coating locally, as for instance, by the blow of the type in a typewriter or by a suitable scriber tool, and in the places where the coating has been removed, the ink can penetrate the fine paper sheet. This demands a degree of plasticity in the coating, which, in the case of a protein coating was attained by means of suitable softening agents added to the protein.

Thus stencils are known in which glycerine has been added to the protein to give the desired softening effect. The softening agent is soluble in water and before the stencil can be used it has to be moistened to enable the protein coat to be readily removed by the impact of the type. The stencil sheet must therefore be inserted in the typewriter in a moist state, an exceedingly diflicult and delicate operation. Further, the mosit sheet causes the typewriter parts to rust and the impressions obtained are lacking in uniformity over the entire page, owing to the fact that the stencil sheet dries off during the preparation of the stencil and the case with which the coating is removed varies with the degree of moistness of the sheet. For the reasons stated such protein coated stencils have not hitherto been favoured by users.

It has also been proposed to avoid the necessity of moistening the sheets by adding a softener to the protein before coatinga usual softener used for this purpose has been soap or the like. When exposed to the air however, such agents become ineffective and the protein coating cannot be readily removed by the type after such sheets have been kept in storage for some days. \Vhen Serial No. 76,337, and in Germany March 16, 1925.

such sheets have been kept for a time the coating adheres so firmly to the paper sheet that when closed letters, such 0, O, c, d, b

and the like are struck, the-centre part is re successful more especially as some duplicat ing inks tend to make the protein coating sticky during the process of pulling off the copies and the result is that after the first few copies, the pulls obtained are apt to be smudged and unusable.

According to the present invention these difficulties, hitherto associated with protein covered or coated stencil sheets are avoided by applying an additional thin elastic coatmgto the protein coated sheet immediately after the protein coating has been applied to the sheet of paper. The purpose of this additional coating is to protect the protein coating from the action of the air and pre serve it in a state ready for use. The additional coating may be applied to both sides of the paper sheet, asfor instance by dips ping the protein coated sheet in a bath of the a protective coating material in liquid form.

By means of this invention the protein coating is very readily removed and an excellently clear outline is obtained. Suitable agents, such as hardening agents, may be quent stickiness of the stencil face avoided.

The. stencil sheets prepared in accordance with this invention can be used in the typewriter or be prepared by means of a suitable hand tool without any previous preparation or treatment. They produce very clear copies in large numbers and also permit large sized sheets to be used. Furthermore, they can be kept in stock for long periods without deterioration.

The most suitable coating which it is preferred to employ is a collodion solution.

In carrying the invention into effect, the stencil sheet immediately after it has been coated with protein in the usual manner is coated with a suitably thinned solution of collodion in ether or alcohol or a mixture of these, It will be understood that other materials having similar properties may be employed in place of collodion, these properties being to form a thin elastic skin which resists the atmosphere. When it is desired to add to the protective coating reagents modifying the protein t. i. a coagulating agent, it. is necessary to choose one which.

is soluble in an ether-alcohol mixture, the usual solvent for collodion. Suitable coagulating agents which satisfythis requirement are tannin or formaldehyde dissolved in alcohol or the solution of formaldehyde in methyl-alcohol generally known in the market by the name of Holzin. When the protective coating is formed of a substance other than collouion, the coagulating agent or agents chosen will be dctcrminedby the solvent used for the said coating. The coating may be applied in any well known manner, as by passing a web of the protein paper straight from its coating bath to abath of the'collodion or other-protective coating in thin liquid form or the coating may be applied by transfer rollers between which the web of stencil sheeting is passed.

1. A duplicating stencil paper having a fine permeable paper body, a coating of protein on said body and a protective coating of an elastic substance impervious to atmospheric action and having the quality to preventhardcning of the protein coating.

2. A duplicate stencil sheet having a fine paper body, a coating of protein on said body, an elastic coating over said protein -coating, said elastic coating being impervious to the atmosphere and having the quality to prevent hardening of the protein coaeting, and an agent for coagulating the protein embodied in said elastic coating.

3. A duplicating stencil paper having a fine permeable paper body, a coating of protein on said body and a protective'coating of collodion which adheres to said protein coating.

4. A duplicating stencil paper having a fine paper body permeable to ink, a coating of protein on said body, and a protective coating over said protein coating and composed of collodion and a coagulating agent composed of tannin embodied in said collodion coatin I 5. A duplicating stencil paper having a permeable fine paper body, a coating of protein on said body and a protective coating having a colouring material and a coagulating agent embodied therein, said protective coating being superposed directly on the protein coating and being impervious to the atmosphere and elastic 6. The method of making stencil paper which consists in, applying a coat of protein to a thin permeable paper web, passing said web imn iediately to a bath of a protective coating in thinliquid form to coat both surfaces of said web and cutting stencil sheets from said Web.

7. The method of making stencil paper which consists of passing a thin permeable paper Web to a protein bath tocoat both surfaces of said Web therewith and immediately thereafter coating the said protein layerwith a protective covering of a thin solution of collodion having the properties of protecting the protein coating against hardening and atmospheric conditions.

In testimony whereof I affix my signature.

HEINRICH HARTMANN. 

